Mark Tarnopolsky, a professor of pediatrics and medicine at McMaster University in Hamilton, Ontario, remembers clearly a patient he saw more than a decade ago, when he first began specializing in metabolism and nutrition.

The patient was an 8-year-old boy who had rapidly become weak and eventually almost completely paralyzed after exercising. His muscles were breaking down, spilling a protein known as myoglobin into the blood and threatening the survival of the boy’s kidneys, if not of the child himself.

*Note: In the print edition of Quest, this article was titled "Rounding Up the Usual -- and Not So Usual -- Suspects."

The scene is familiar to everyone who watches crime dramas. The safe has been opened, and the hotel guests' jewelry and other valuables are missing. What happened, and when, and who's responsible?